Question

Which of the following statements about the spontaneous reaction occurring in a galvanic cell is always true?
(A) ${E^o}_{cell}>0,\mathrm{\Delta }{G}^0<0$ and $Q<K$
(B) ${E^o}_{cell}>0,\mathrm{\Delta }{G}^0<0$ and $Q>K$
(C) ${E^o}_{cell}>0,\mathrm{\Delta }{G}^0>0$ and $Q<K$
(D) $E_{cell}>0,\mathrm{\Delta }{G}^0<0$ and $Q<K$

Answer 1

Hint: A galvanic cell is a device that can generate electric energy from chemical energy. Electrical energy brings out a chemical reaction with the help of an external energy source. Both the anode and cathode are in the same container with an electrolyte solution. The reaction which produces electricity in a galvanic cell is spontaneous.

Complete Solution :
In a galvanic cell, the standard electrode potential for redox reaction is positive than the reaction in the galvanic cell proceeds in the forward direction, which is known as a spontaneous process in a galvanic cell.
For standard electrochemical cells,
The standard electrode potential of a redox reaction is positive means, ${E^o}_{cell}>0$-- (1)
Spontaneous redox reactions in a galvanic cell can be used to produce electricity.
In a galvanic cell, the relation between Gibbs free energy and standard emf of a cell,
$\mathrm{\Delta }{G}^0=-nF{E^0}_{cell}$
Here, n = number of moles, F = faraday constant

If ${E^o}_{cell}>0$, then $\mathrm{\Delta }{G}^o<0$ which indicates the process in a galvanic cell is spontaneous.
If $\mathrm{\Delta }{E}^o<0$ , then $\mathrm{\Delta }{G}^o>0$ which represents the process in an electrolytic cell is non-spontaneous.
Hence, in a galvanic cell, the change in Gibbs free energy is positive when a spontaneous redox reaction drives the cell to produce an electric potential.
If the reaction is spontaneous then Q < K
So, the spontaneous reaction occurring in a galvanic cell is ${E^o}_{cell}>0,\mathrm{\Delta }{G}^0<0$ and $Q<K$
So, the correct answer is “Option A”.

Note: If the standard emf of a cell is negative, then the reaction will not proceed in the forward reaction which indicates a non-spontaneous process. These reactions will be a spontaneous reaction in the reverse direction and non-spontaneous redox reactions cannot produce the electricity.